FileZilla is powerful Open Source FTP/SFTP client with many features. It has been designed for ease of use and with support for as many features as possible, while still being fast and reliable.

The main features of FileZilla are:
Ability to resume Uploads/Downloads (if the server supports it)
Custom Commands
Site Manager with folders
Keep Alive system
Timeout detection
Firewall support
SOCKS4/5 and HTTP1.1 Proxy support
SSL secured connections
SFTP support
Upload/Download Queue
Drag&Drop
Multi-language support
GSS authentication and encryption using Kerberos